During a production process of a display panel, a glass substrate as a base is transferred many times between various separated production devices due to the complicated process and too many manufacturing steps. In an actual manufacturing process, a cassette for carrying a plurality of glass substrates is usually used as a carrying device for storing and transferring the glass substrate. Therefore, quality and specification standards of the substrate cassette become key factors ensuring stable placing and picking of the glass substrate.
During the production process, if supporting brackets in the substrate cassette are not horizontal or errors in relative positions thereof are large, it is likely to cause damage to the glass substrate. However, in the prior art, there has not been a device for detecting the positions of the supporting brackets in the substrate cassette yet.